Barnard’s star has at least one planet orbiting it after all

A red dwarf star known as Barnard’s star, which lies a mere six light-years from our solar system, has at least one — and possibly a handful — of small rocky planets orbiting it, a new study suggests.

Barnard’s star, which is about one-sixth the mass of our sun, is the closest individual star to our solar system. Only the three stars in the Alpha Centauri system are closer. Due to its proximity to Earth, Barnard’s star has long been a target of astronomers looking for exoplanets (SN: 12/1/73, SN: 12/7/23).

Now, after several false starts over the decades, researchers may finally have hit pay dirt. Jonay González Hernández, an astrophysicist at the Instituto de Astrofísica de Canarias in Tenerife, Spain, and his team scrutinized more than 150 observations made by a telescope in South America over the course of four years. Specifically, they looked for tiny wobbles that would betray the presence of planets gravitationally yanking the star to and fro as they orbited.

The strongest wobble takes place every 3.15 days, the team reports online October 1 in Astronomy & Astrophysics. It probably is caused by the near-circular orbit of a small rocky planet about three times the mass of Mars, says González Hernández.

The researchers have done a good job of excluding other possible sources of the wobble, such as rotation of the star or movement of the telescope during observations, says astronomer Jennifer Burt. Those efforts, plus the high precision of the instruments used to collect the team’s data, “will convince scientists that this discovery is real,” notes Burt, of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. That, in turn, should inspire other teams to revisit all of the past observations that they’ve made of Barnard’s star.

Indeed, the new study suggests that there are more discoveries to be made. González Hernández and his colleagues have noted smaller oscillations that are superimposed on the larger wobble. Although they are yet to be confirmed, they likely represent the presence of three smaller orbs circling the star at periods of 2.34 days, 4.12 days and 6.74 days. All four of these purported planets are too close to Barnard’s star to support life as we know it, the researchers suggest